The present invention relates to truck covers and more particularly to tensioning apparatus to aid in securing such a cover during transit.
Open top receptacles such as those used on dump trucks and roll-off trash dumpsters often contain loads which can be easily agitated by forces from bumpy roads, external winds, and the airstream created by vehicular movement. Accordingly, a flexible cover is often secured on top of these receptacles to shield the contents. Since such receptacles are often up to 40 feet long and as wide as the vehicle upon which they are carried, the covers tend to be large and unwieldy. Some form of mechanical assistance is often used to manipulate and secure such covers.
Simple truck cover manipulators are often comprised of a pair of pivoting arms connected to a crossbar perpendicular to the long dimension of the receptacle. The crossbar can then draw such a cover longitudinally from a rolled or furled position across the open top, as disclosed in U.S. Pat. No. 4,157,202, issued to Applicant. However, the rolled or furled position of the cover is usually on a cab shield, which is a horizontal surface elevated with respect to the top edge of the receptacle. As the cover is drawn over the load, usually in an arcuate path, there is a tendency for wind which may flow across or beneath the cover to cause billowing and flapping. After the drawn cover is secured, elevated mounting position of the cover on the raised cab shield continues to promote a persistent void under the cover during transit. Such a void allows wind to continue to flow beneath the cover and cause further billowing and flapping, accelerating cover wear and causing excessive stress in the cover manipulator mechanism. Cover wear and fatigue in the cover manipulator members also degrades the effectiveness of the cover in securing the load.
Previous advancements in the methods used to minimize wind agitation of the cover during deployment and transit include flush mounted covers and telescoping arms to linearize the arcuate path of the covering mechanism, as disclosed by U.S. Pat. Nos. 5,179,991 and 5,340,187 respectively, both issued to Applicant.
Flush mounted covers typically use guides mounted on the lip along the top longitudinal edges of the receptacle. Often, however, the sides of the receptacle become bowed from the outward force of the load within the receptacle such that the guides are no longer parallel. Also, the guides on the lip of the receptacle tend to be subject to clogging and physical damage from being struck by dense loads and heavy equipment during loading. Further, flush mounted covers require that the entire load be below the upper edge of the receptacle to allow sufficient clearance for closing the cover. Finally, flush mounted covers require that the top of all sides be at the same height, and therefore is unsuited to a receptacle with a raised cab shield at the forward edge.
Telescoping arms to draw the cover over the load require complex moving parts and sophisticated controls for the mechanical arms, which tends to increase production and maintenance costs. They also share the problem of load clearance, as the entire load must be below the path of the closing arms.
Other methods to aid in securing the cover include a second crossbar and pair of arms attached to the main arm apparatus, as suggested by U.S. Pat. No. 5,031,955, issued to Searfoss, and a second crossbar to adapt the cover to different height receptacles, as suggested by U.S. Pat. No. 5,388,882, issued to Russell.
The Searfoss approach, however, increases the fatigue on the main pair of arms by mounting the second pair of arms thereto. Further, as the second pair of arms are almost as long as the main pair, they are likewise subject to fatigue as wind agitates the cover.
The Russell approach directs the forward edge of the cover such that it is lower than the receptacle on which the cover rests. Accordingly, Russell uses a manual valve control tied into the vehicle's air system to effect operator assisted manipulation to match the height to the receptacle to be covered. Therefore, such apparatus is not a stand-alone automated mechanism since it requires manual operator intervention and need be powered by a host vehicle.
Therefore, the prior art fails to provide a mechanically simple, independently mounted, flexible cover mechanism which enables the complete and secure coverage of loads which may extend above the body of the receptacle to be covered.